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HomeMy WebLinkAbout03647 - Technical Information Report - Preliminary GeotecfnicaCEngineering Associated Earth Sciences, Inc. �U . Serving the Pacific Northwest Since 1981 • Subsurface Exploration, Geologic Hazards, and Preliminary Geotechnical Engineering Report Water Resources NELSEN MIDDLE SCHOOL _, % IMPROVEMENTS j Renton, Washington ifs If Foiw Prepared for EnvironmentaC.Assessments and Remediation Renton School District c/o Greene-Gasaway, PLLC '1 ' Project No. KE110083A May 16, 2011 SustainabCe DeveCopment Services •i } Geologic Assessments 3404/7 SUBSURFACE EXPLORATION, GEOLOGIC HAZARDS, AND PRELIMINARY GEOTECHNICAL ENGINEERING REPORT NELSEN MIDDLE SCHOOL IMPROVEMENTS Renton, Washington Prepared for: Renton School District c/o Greene-Gasaway, PLL,C P.O. Box 4158 Federal Way, Washington 98063 Prepared by: Associated Earth Sciences, Inc. 911 5th Avenue, Suite 100 Kirkland, Washington 98033 425-827-7701 Fax: 425-827-5424 May 16, 2011 Project No. KE110083A Subsurface Exploration, Geologic Hazards, and Nelsen Middle School Improvements Preliminary Geotechnical Engineering Report • Renton, Washington Project and Site Conditions I. PROJECT AND SITE CONDITIONS 1.0 INTRODUCTION This report presents the results of our subsurface exploration, geologic hazards, and preliminary geotechnical engineering studies for the proposed improvements at Nelsen Middle School. The location of the site is presented on the "Vicinity Map," Figure 1. The approximate locations of exploration borings completed for this study are shown on the "Site and Exploration Plan," Figure 2. Logs of the subsurface explorations completed for this study and copies of laboratory testing results are included in the Appendix. 1.1 Purpose and Scope The purpose of this study was to provide geotechnical engineering recommendations to be utilized in the preliminary design of the project. This study included a review of selected available geologic literature, advancing 13 exploration borings, and performing geologic studies to assess the type, thickness, distribution, and physical properties of the subsurface sediments and shallow ground water. Grain size analysis and moisture content laboratory tests were completed on selected soil samples recovered from our exploration borings. Geotechnical engineering studies were completed to establish preliminary recommendations for the type of suitable foundations and floors, allowable foundation soil bearing pressure, anticipated foundation and floor settlement, permeable and conventional pavement recommendations, and drainage considerations. This report summarizes our fieldwork and offers preliminary recommendations based on our present understanding of the project. We recommend that we be allowed to review the recommendations presented in this report and revise them, if needed, when a project design has been finalized. 1.2 Authorization Authorization to proceed with this study was granted by the Renton School District by means of Purchase Order #2011000115. Our work was completed in general accordance with our scope of work and cost proposal, dated March 21, 2011. This report has been prepared for the exclusive use of the Renton School District (RSD), and its agents, for specific application to this project. Within the limitations of scope, schedule, and budget, our services have been performed in accordance with generally accepted geotechnical engineering and engineering geology practices in effect in this area at the time our report was prepared. No other warranty, express or implied, is made. May 16, 2011 ASSOCIATED EARTH SCIENCES, INC. JPLJ I,/Id-KE110083A3-Projects1101100931KE1 WP Page 1 Subsurface Exploration, Geologic Hazards, and Nelsen Middle School Improvements Preliminary Geotechnical Engineering Report Renton, Washington Project and Site Conditions 2.0 PROJECT AND SITE DESCRIPTION Project plans were under development at the time this report was prepared. Based on our discussions with Greene-Gasaway, PLLC, we understand that the project will consist of a substantial site renovation, with site improvements consisting of replacing some of the existing paving with permeable asphalt pavement, constructing two new baseball fields and one new soccer field, and installing a new storm water handling facility. We understand that infiltration is currently under consideration for the handling of storm water runoff. We anticipate that new structures and paving can be constructed close to existing grades, with typical cuts and fills of less than about 5 feet to achieve finished grade. Our previous work on the site included construction monitoring services in 1999 for building additions and new pavement areas to the north and west of the main building. Based on this previous work and our review of the published geologic map, we anticipated that the site is underlain by fill overlying glacially consolidated Vashon till deposits. The existing school includes a main building on the southeast part of the site, with athletic facilities to the north and west, and paved parking areas to the south, northeast, and west of the main building. Site topography is relatively flat to gently sloping, with sloped grassy "steps" which lead downward to the north and west to existing sports field areas. The ground surface continues steeply downward from the subject site, approximately 15 to 20 vertical feet to the north and roughly 25 vertical feet to the west, to nearby properties. A wooded stream corridor with areas of ponded water lies to the east. 3.0 SUBSURFACE EXPLORATION Our subsurface exploration completed for this project included advancing 13 exploration borings. The conclusions and recommendations presented in this report are based on the explorations completed for this study. Additional sources of geotechnical data are discussed in the "Subsurface Conditions" section of this report. The locations and depths of the explorations were completed within site and budget constraints. 3.1 Exploration Borings The exploration borings were completed by advancing hollow-stem auger tools with a track- mounted drill rig. During the drilling process, samples were obtained at generally 2.5- to 5- foot-depth intervals. The exploration borings were continuously observed and logged by a representative from our firm. The exploration logs presented in the Appendix are based on the field logs, drilling action, and inspection of the samples secured. Disturbed but representative samples were obtained by using the Standard Penetration Test (SPT) procedure in accordance with American Society for Testing and Materials May 16, 2011 ASSOCIATED EARTH SCIENCES, INC. JPLJtb/id-KEI10083A3-Projects1201100831KE1WP Page 2 Subsurface Exploration, Geologic Hazards, and Nelsen Middle School Improvements Preliminary Geotechnical Engineering Report • Renton, Washington Project and Site Conditions (ASTM):D-1586. This test and sampling method consists of driving a standard 2-inch outside- diameter, split-barrel sampler a distance of 18 inches into the soil with a 140-pound hammer free-falling a distance of 30 inches. The number of blows for each 6-inch interval is recorded, and the number of blows required to drive the sampler the final 12 inches is known as the Standard Penetration Resistance ("N") or blow count. If a total of 50 is recorded within one 6-inch interval, the blow count is recorded as the number of blows for the corresponding number of inches of penetration. The resistance, or N-value, provides a measure of the relative density of granular soils or the relative consistency of cohesive soils; these values are plotted on the attached exploration boring logs. The samples obtained from the split-barrel sampler were classified in the field and representative portions placed in watertight containers. The samples were then transported to our laboratory for further visual classification and laboratory testing, as necessary. Observation Well Installation An observation well was placed in exploration boring EB-9 at the time of drilling to determine if a static ground water level was present and to measure its depth. On April 21, 2011, a static water level was measured at a depth of 33.81 feet. 3.2 Laboratory Tests Laboratory test results are included in the Appendix. The following laboratory tests were completed for this project: • Three mechanical grain size analyses by ASTM:D-422 and D-1140 • Two percent passing the No. 200 sieve by ASTM:D-1140 • Five moisture content tests by ASTM:D-2216 4.0 SUBSURFACE CONDITIONS Subsurface conditions at the project site were inferred from the field explorations accomplished for this study, visual reconnaissance of the site, and review of selected applicable geologic literature. We also reviewed field reports completed by Associated Earth Sciences, Inc. (AESI) during construction of an earlier renovation of Nelsen Middle School in 1999. Because of the nature of exploratory work below ground, extrapolation of subsurface conditions between field explorations is necessary. It should be noted that differing subsurface conditions may sometimes be present due to the random nature of deposition and the alteration of topography by past grading and/or filling. The nature and extent of any variations between the field explorations may not become fully evident until construction. May 16, 2011 ASSOCIATED EARTH SCIENCES, INC. JPL/tb/Id-KEI10083A3-Projects120110083IKEIWP Page 3 Subsurface Exploration, Geologic Hazards, and Nelsen Middle School Improvements Preliminary Geotechnical Engineering Report Renton, Washington Project and Site Conditions • 4.1 Stratigraphy Fill Existing fill was encountered in all exploration borings except for EB-1, EB-2, and EB-5. The fill ranged in thickness from 4 to 31 feet within our explorations and consisted of loose to medium dense silty sand with gravel and scattered organics. Figure 2 shows the depth of fill encountered at each boring location. Existing fill is not suitable for structural support. Existing fill should be removed from below planned structure areas, and should be recompacted under paving and athletic fields, especially if synthetic turf is planned. Existing fill is discussed in greater detail in the "Site Preparation" section of this report. Stratified Drift Sediments (undifferentiated) All of our explorations encountered medium dense to very dense brownish gray silty sand with gravel and sand lenses and beds, with thick sand beds encountered in exploration borings EB-5 and EB-9. As indicated above and described below, our previous work at the site and our review of the published geologic map indicate that the site is expected to be underlain by glacially-consolidated soils, likely lodgement till; however, the sediments we observed were not typical of lodgement till sediments. The site sediments were somewhat more sorted and, in places, more stratified than typical lodgement till sediments, although that is the locally common sedimentary unit they most closely resemble. Lodgement till typically possesses high- strength and low-compressibility attributes that are favorable for support of foundations, floor slabs, and paving, with proper preparation. The site soils are silty and moisture-sensitive. In the presence of moisture contents above the optimum moisture content for compaction purposes, the site soils can be easily disturbed by vehicles and earthwork equipment. Careful management of moisture-sensitive soils, as recommended in this report, will be needed to reduce the potential for disturbance of wet native soils and costs associated with repairing disturbed soils. Weathered Tertiary Bedrock At the location of exploration boring EB-3, the stratified drift was underlain by a highly fractured silty sand with gravel, which appeared as "chips" in the sampler. We interpret this material to be representative of weathered Tertiary bedrock. Due to the relatively weak induration of the weathered rock, the description of the rock on the attached exploration log is similar to those used to describe soils. Where encountered, the weathered bedrock extended beyond the depth explored. • Existing Geotechnical Data by AESI (1999) We reviewed several construction field reports for work completed on-site in 1999. Our field reports addressed observation of bearing soils and compaction testing on shear wall foundations May 16, 2011 ASSOCIATED EARTH SCIENCES, INC, !PL/th/Id-KE110083A3-Projeas1201100831KEIWP Page 4 Subsurface Exploration, Geologic Hazards, and Nelsen Middle School Improvements Preliminary Geotechnical Engineering Report • Renton, Washington Project and Site Conditions within several classrooms. We also performed compaction testing on the subgrade for new parking areas. Soils described in these field reports are generally consistent with our current exploration borings. Published Geologic Map We reviewed a published geologic map of the area (Geologic Map of King County, Washington, by Derek B. Booth, Kathy A. Troost, and Aaron P. Wisher, 2006). The referenced map indicates that the site vicinity is characterized primarily by lodgement till at the ground surface, with small exposures of Tertiary bedrock nearby. It is not unusual to find localized areas that vary from published regional scale geologic mapping, and that is the case with the stratified drift described at this site. We recommend that design activities for this project be based on subsurface materials observed in our on-site explorations 4.2 Hydrology Ground water seepage was encountered in a thick sand bed in exploration boring EB-9 at the time of drilling, and we installed a plastic open-standpipe piezometer in EB-9 to allow measurement of ground water levels after drilling was completed. Observed ground water conditions are presented on exploration logs included in the Appendix. In addition, moist to wet soil was encountered at various depths within the existing fill, suggesting that perched ground water should be expected throughout the site. Perched ground water occurs where vertical infiltration of surface water is impeded by lower-permeability soil units at depth, and water tends to move laterally above the perching layer. If construction takes place during the summer, we do not anticipate significant dewatering will be necessary. However, during the winter months, dewatering in the form of pumping and/or trenching may be necessary to collect seepage from excavations. Ground water conditions should be expected to vary due to changes in season, precipitation, on- and off-site land usage, and other factors. 4.3 Infiltration Potential/Permeable Pavement Considerations Our explorations encountered shallow materials that consisted of fill over stratified drift. The existing fill at EB-13, located at the proposed permeable pavement area at the west parking lot, classifies as sandy loam on the United States Department of Agriculture (USDA) textural soil triangle. Much of the underlying drift is silty, and the drift has been consolidated by glaciers, which limits its potential for use as an infiltration receptor. Wet soil, suggestive of perched ground water, was observed to vary in depth, but was often relatively shallow, which can also be a limiting factor that can be difficult or impossible to overcome. In the areas proposed for permeable pavement, adequate storage of infiltrating storm water will need to be incorporated into the pavement sections. We recommend that permeable pavement areas be provided with May 16, 2011 ASSOCIATED EARTH SCIENCES, INC. JPL/th/ld-KEI/003343-Projects120110O831KEIWP Page 5 Subsurface Exploration, Geologic Hazards, and Nelsen Middle School Improvements Preliminary Geotechnical Engineering Report Renton, Washington Project and Site Conditions either underdrains or a conventional surface water collection system to collect available water when rainfall exceeds the storage capacity and infiltration capacity of the permeable pavement system. In general, we conclude that the potential for storm concentrated water disposal by means of infiltration is very limited at this site. As stated above, we installed a monitoring well extending below the fill and into a thick sand bed at the location of exploration boring EB-9, and measured ground water at 33.81 feet below the ground surface on April 21, 2011. Grain-size analyses performed on samples taken at 25 and 30 feet in EB-9 suggest that a suitable thickness of receptor soil for a deep discharge/injection well-type system may exist above the observed ground water. Our borings did not verify the lateral extent of the potential storm water receptor, and such verification is an important component of the viability of the potential receptor. Steep slopes located to the north and west of the subject site, likely capped with a thick fill zone (as encountered in EB-8 an EB-9), also warrant additional study if a deep infiltration system is considered. Additional studies to support an infiltration design may also include additional explorations, consultation, or off-site ground water fate and transport studies, including at the residential property located at the bottom of the steep slope to the west of the subject site. May 16, 2011 ASSOCIATED EARTH SCIENCES, INC. JPLJtb/1A-KE/10083A3-Projects120110083IKEIWP Page 6 Subsurface Exploration, Geologic Hazards, and Nelsen Middle School bnprovements Preliminary Geotechnical Engineering Report • Renton, Washington Geologic Hazards and Mitigations II. GEOLOGIC HAZARDS AND MITIGATIONS The following discussion of potential geologic hazards is based on the geologic, slope, and ground and surface water conditions, as observed and discussed herein. The discussion will be limited to slope stability, seismic, and erosion issues. It should be noted that the City of Renton Sensitive Areas mapping and the King County IMAP website show the site as lying within a known coal mine hazard area, with the Renton Sensitive Areas map designating the coal mine hazard as "moderate." Based on the presence of existing development at and surrounding the subject site, we anticipate that the requirements for a detailed coal mine hazard study may be waived, per RMC 4-3-050(D)(4)(b)(i)(c). We are available to provide a detailed coal mine hazard assessment for the project, if requested. 5.0 SLOPE HAZARDS AND MITIGATIONS Existing slopes on the site are moderately inclined and do not have visual indications of instability or unusually intense erosion. The slopes leading downward to the west and north of the subject site are steep and, based on the exploration borings completed nearby, likely include loose to medium dense fill material. These off-site slopes appear to be greater than forty percent, placing them into the "high landslide hazard" category per RMC 4-3- 050(J)(1)(b)(iii). However, these slopes did not show signs of instability at the time of our exploration. Therefore, in our opinion, the proposed improvements should not negatively impact the slopes or cause instability of these slopes provided that storm water from the proposed permeable pavement area is not allowed to discharge over the slope faces. Similarly, if conventional pavement is used, storm water should not be directed to the steep slope areas. If a detention pond is planned in the area of these slopes, it will likely be excavated in fill and will need to be lined to prevent leakage into the slope soils. 6.0 SEISMIC HAZARDS AND MITIGATIONS The following discussion is a general assessment of seismic hazards that is intended to be useful to the school district in terms of understanding seismic issues, and to the structural engineer for preliminary structural design. In our opinion, the site does not include areas that meet the City of Renton definition for Seismic Hazard areas. Earthquakes occur regularly in the Pugat Lowland. The majority of these events are small and are usually not felt by people. However, large earthquakes do occur, as evidenced by the 1949, 7.2-magnitude event; the 2001, 6.8-magnitude event; and the 1965, 6.5-magnitude event. The 1949 earthquake appears to have been the largest in this region during recorded history and was centered in the Olympia area. Evaluation of earthquake return rates indicates May 16, 2011 ASSOCIATED EARTH SCIENCES, INC. JPL./tb/1d-KE110083A3-Projects120110083IKEIWP Page 7 Subsurface Exploration, Geologic Hazards, and Nelsen Middle School bnprovements Preliminary Geotechnical Engineering Report Renton, Washington Geologic Hazards and Mitigations • that an earthquake of the magnitude between 5.5 and 6.0 is likely within a given 20-year period. Generally, there are four types of potential geologic hazards associated with large seismic events: 1) surficial ground rupture, 2) seismically induced landslides, 3) liquefaction, and 4) ground motion. The potential for each of these hazards to adversely impact the proposed project is discussed below. 6.1 Surficial Ground Rupture Generally, the largest earthquakes that have occurred in the Puget Sound area are sub-crustal events with epicenters ranging from 50 to 70 kilometers in depth. Earthquakes that are generated at such depths usually do not result in fault rupture at the ground surface. However current research indicates that surficial ground rupture is possible in the Seattle Fault Zone. The Seattle Fault Zone is an area of active research. Our current understanding of this fault zone is poor, and actively evolving. The site is located approximately 5 miles south of the currently mapped limits of the Seattle Fault Zone. Due to the fact that the site lies outside of the currently understood limits of the Seattle Fault Zone, the risk of damage to the project as a result of surficial ground rupture is low, in our opinion. 6.2 Seismically Induced Landslides Existing slopes on the site are moderately inclined and do not have visual indications of instability or unusually intense erosion. The slopes leading downward to the west and north of the subject site are steep and, based on the exploration borings completed nearby, likely include loose to medium dense fill material. However, these slopes did not show signs of instability at the time of our exploration. Considering the history of adequate slope stability performance on-site, and the fact that no new buildings are proposed as part of the project, the risk to the project from seismically induced landslides is low, in our opinion. Storm water should be collected and routed away from sloping areas. If a detention pond is planned in the area of these slopes, it will likely be excavated in fill and will need to be lined to prevent leakage into the slope soils. 6.3 Liquefaction Liquefaction is a process through which unconsolidated soil loses strength as a result of vibrations, such as those which occur during a seismic event. During normal conditions, the weight of the soil is supported by both grain-to-grain contacts and by the fluid pressure within the pore spaces of the soil below the water table. Extreme vibratory shaking can disrupt the grain-to-grain contact, increase the pore pressure, and result in a temporary decrease in soil shear strength. The soil is said to be liquefied when nearly all of the weight of the soil is supported by pore pressure alone. Liquefaction can result in deformation of the sediment and settlement of overlying structures. Areas most susceptible to liquefaction include those areas May 16, 2011 ASSOCIATED EARTH SCIENCES, INC. 1PL/rb/1d-KEl10083A3-Projects120!/00831KEIWP Page 8 Subsurface Exploration, Geologic Hazards, and Nelsen Middle School Improvements Preliminary Geotechnical Engineering Report Renton, Washington Geologic Hazards and Mitigations underlain by non-cohesive silt and sand with low relative densities, accompanied by a shallow water table. The subsurface conditions encountered at the site pose low risk of liquefaction due to relatively high density and lack of an extensive shallow ground water table. No detailed liquefaction analysis was completed as part of this study, and none is warranted, in our opinion. 6.4 Ground Motion It is our opinion that any earthquake damage to the proposed structures, when founded on suitable bearing strata in accordance with the recommendations contained herein, will be caused by the intensity and acceleration associated with the event and not any of the above- discussed impacts. Structural design should follow 2009 IBC standards using Site Class "C" as defined in Table 1613.5.2. The 2009 IBC seismic design parameters for short period (Ss) and 1-second period (SI) spectral acceleration values were determined from the latitude and longitude of the project site using the United States Geological Survey (USGS) National Seismic Hazard Mapping Project website (http://earthquake.usgs.gov/hazmaps/). These values are based on Site Class "B". Based on 2002 data, the USGS website interpolated ground motions at the project site to be 1.399g and 0.632g for building periods of 0.2 and 1.0 seconds, respectively, with a 2 percent chance of exceedance in 50 years. These values correspond to site coefficients Fa = 1.00 and Fy = 1.322, and a peak ground acceleration of 0.373g. The Fa, Fy, and peak horizontal acceleration values have been corrected for Site Class "C" in accordance with the IBC. 7.0 EROSION HAZARDS AND MITIGATIONS The following discussion addresses Washington State Department of Ecology (Ecology) erosion control regulations that will be applicable to the project. The subject site does not lie within an erosion hazard area as mapped in the City of Renton "Erosion Hazards" map. Also, the site soils are characterized by the Natural Resource Conservation Service as having slight erosion potential. This characterization translates to a "Low Erosion Hazard" designation by the City of Renton Municipal Code. However, the site is underlain by silty fill and drift sediments. Therefore, the erosion potential of the site soils is high, especially within the sloping areas of the site. As of October 1, 2008, the Ecology Construction Storm Water General Permit (also known as the National Pollutant Discharge Elimination System [NPDES] permit) requires weekly Temporary Erosion and Sedimentation Control (TESC) inspections and turbidity monitoring for all sites 1 or more acres in size that discharge storm water to surface waters of the state. Because we anticipate that the proposed project (field improvements) will require disturbance of more than 1 acre, we anticipate that these inspection and reporting requirements will be May 16, 2011 ASSOCIATED EARTH SCIENCES, INC. JPL/tb/Id-KEI10083A3-Projects1201100831KEIWP Page 9 Subsu,face Exploration, Geologic Hazards, and Nelsen Middle School Improvements Preliminary Geotechnical Engineering Report Renton, Washington Geologic Hazards and Mitigations triggered. The following recommendations are related to general erosion potential and mitigation. The TESC inspections and turbidity monitoring of runoff must be completed by a Certified Erosion and Sediment Control Lead (CESCL) for the duration of the construction. The weekly TESC reports do not need to be sent to Ecology, but should be logged into the project Storm Water Pollution Prevention Plan (SWPPP). Ecology requires a monthly summary report of the turbidity monitoring results signed by the NPDES permit holder. If the monitored turbidity equals or exceeds 25 nephelometric turbidity units (NTU) (Ecology benchmark standard), the project best management practices (BMPs) should be modified to decrease the turbidity of storm water leaving the site. Changes and upgrades to the BMPs should be documented in the weekly TESC reports and continued until the weekly turbidity reading is 25 NTU or lower. If the monitored turbidity exceeds 250 NTU, the results must be reported to Ecology via phone within 24 hours and corrective actions should be implemented as soon as possible. Daily turbidity monitoring is continued until the corrective actions lowers the turbidity to below 25 NTU, or until the discharge stops. This description of the sampling benchmarks and reporting requirements is a brief summary of the Construction Storm Water General Permit conditions. The general permit template is available on the internee. In order to meet the current Ecology requirements, a properly developed, constructed, and maintained erosion control plan consistent with City of Renton standards and best management erosion control practices will be required for this project. AESI is available to assist the project civil engineer in developing site-specific erosion control plans. Based on past experience, it will be necessary to make adjustments and provide additional measures to the TESC plan in order to optimize its effectiveness. Ultimately, the success of the TESC plan depends on a proactive approach to project planning and contractor implementation and maintenance. The most effective erosion control measure is the maintenance of adequate ground cover. Maintaining cover measures atop disturbed ground provides the greatest reduction to the potential generation of turbid runoff and sediment transport. During the local wet season (October 151 through March 3151), exposed soil should not remain uncovered for more than 2 days unless it is actively being worked. Ground-cover measures can include erosion control matting, plastic sheeting, straw mulch, crushed rock or recycled concrete, or mature hydroseed. Surface drainage control measures are also essential for collecting and controlling the site runoff. Flow paths across slopes should be kept to less than 50 feet in order to reduce the erosion and sediment transport potential of concentrated flow. Ditch/swale spacing will need to be shortened with increasing slope gradient. Ditches and swales that exceed a gradient of about 7 to 10 percent, depending on their flow length, should have properly constructed check http://www.ecy.wa.gov/programs/wq/stormwater/construction/constructionfinalpermit.pdf May 16, 2011 ASSOCIATED EARTH SCIENCES, INC. JPL/,b//d-KE110083A3-Projecrs120110083IKEIWP Page 10 Subsurface Exploration, Geologic Hazards, and Nelsen Middle School Improvements Preliminary Geotechnical Engineering Report • Renton, Washington Geologic Hazards and Mitigations dams installed to reduce the flow velocity of the runoff and reduce the erosion potential within the ditch. Flow paths that are required to be constructed on gradients between 10 to 15 percent should be placed in a riprap-lined swale with the riprap properly sized for the anticipated flow conditions. Flow paths constructed on slope gradients steeper than 15 percent should be placed in a pipe slope drain. AESI is available to assist the project civil engineer in developing a suitable erosion control plan with proper flow control. With respect to water quality, having ground cover prior to rain events is one of the most important and effective means to maintain water quality. Once very fine sediment is suspended in water, the settling times of the smallest particles are on the order of weeks and months. Therefore, the typical retention times of sediment traps or ponds will not reduce the turbidity of highly turbid site runoff to the benchmark turbidity of 25 NTU. Reduction of turbidity from a construction site is almost entirely a function of cover measures and drainage control that have been implemented prior to rain events. Temporary sediment traps and ponds are necessary to control the release rate of the runoff and to provide a catchment for sand-sized and larger soil particles, but are very ineffective at reducing the turbidity of the runoff. Silt fencing should be utilized as buffer protection and not as a flow-control measure. Silt fencing is meant to be placed parallel with topographic contours to prevent sediment-laden runoff from leaving a work area or entering a sensitive area. Silt fences should not be placed to cross contour lines without having separate flow control in front of the silt fence. A swale/berm combination should be constructed to provide flow control rather than let the runoff build up behind the silt fence and utilize the silt fence as the flow-control measure. Runoff flowing in front of a silt fence will cause additional erosion and usually will cause a failure of the silt fence. Improperly installed silt fencing has the potential to cause a much larger erosion hazard than if the silt fence was not installed at all. The use of silt fencing should be limited to protect sensitive areas, and swales should be used to provide flow control. 7.1 Erosion Hazard Mitigation To mitigate the erosion hazards and potential for off-site sediment transport, we recommend the following: 1. Construction activity should be scheduled or phased as much as possible to reduce the amount of earthwork activity that is performed during the winter months. 2. The winter performance of a site is dependent on a well-conceived plan for control of site erosion and storm water runoff. It is easier to keep the soil on the ground than to remove it from storm water. The owner and the design team should include adequate ground-cover measures, access roads, and staging areas in the project bid to give the selected contractor a workable site. The selected contractor needs to be prepared to implement and maintain the required measures to reduce the amount of exposed May 16, 2011 ASSOCIATED EARTH SCIENCES, INC !PL/tb/ld-KE11008343-Projects1201100831KEIWP Page 11 Subsurface Exploration, Geologic Hazards, and Nelsen Middle School Improvements Preliminary Geotechnical Engineering Report Renton, Washington Geologic Hazards and Mitigations ground. A site maintenance plan should be in place in the event storm water turbidity measurements are greater than the Ecology standards. 3. TESC measures for a given area to be graded or otherwise worked should be installed soon after ground clearing. The recommended sequence of construction within a given area after clearing would be to install sediment traps and/or ponds and establish perimeter flow control prior to starting mass grading. 4. During the wetter months of the year, or when large storm events are predicted during the summer months, each work area should be stabilized so that if showers occur, the work area can receive the rainfall without excessive erosion or sediment transport. The required measures for an area to be "buttoned-up" will depend on the time of year and the duration the area will be left un-worked. During the winter months, areas that are to be left un-worked for more than 2 days should be mulched or covered with plastic. During the summer months, stabilization will usually consist of seal-rolling the subgrade. Such measures will aid in the contractor's ability to get back into a work area after a storm event. The stabilization process also includes establishing temporary storm water conveyance channels through work areas to route runoff to the approved treatment facilities. 5. All disturbed areas should be revegetated as soon as possible. If it is outside of the growing season, the disturbed areas should be covered with mulch, as recommended in the erosion control plan. Straw mulch provides a cost-effective cover measure and can be made wind-resistant with the application of a tackifier after it is placed. 6. Surface runoff and discharge should be controlled during and following development. Uncontrolled discharge may promote erosion and sediment transport. Under no circumstances should concentrated discharges be allowed to flow over the top of steep slopes. 7. Soils that are to be reused around the site should be stored in such a manner as to reduce erosion from the stockpile. Protective measures may include, but are not limited to, covering with plastic sheeting, the use of low stockpiles in flat areas, or the use of silt fences around pile perimeters. During the period between October 151 and March 3151, these measures are required. 8. On-site erosion control inspections and turbidity monitoring (if required) should be performed in accordance with Ecology requirements. Weekly and monthly reporting to Ecology should be performed on a regularly scheduled basis. A discussion of temporary erosion control and site runoff monitoring should be part of the weekly construction team meetings. Temporary and permanent erosion control and drainage measures should be adjusted and maintained, as necessary, for the duration of project construction. May 16, 2011 ASSOCIATED EARTH SCIENCES, INC. MAW-KE110083A3-Projects120110083IKEIWP Page 12 Subsurface Exploration, Geologic Hazards, and Nelsen Middle School Improvements Preliminary Geotechnical Engineering Report • Renton, Washington Geologic Hazards and Mitigations It is our opinion that with the proper implementation of the TESC plans and by field-adjusting appropriate mitigation elements (BMPs) throughout construction, as recommended by the erosion control inspector, the potential adverse impacts from erosion hazards on the project may be mitigated. May 16, 2011 ASSOCIATED EARTH SCIENCES, INC. IPL/rb/Irl-KE110083A3-Projecrs1201100831KE1WP Page 13 Subsurface Exploration, Geologic Hazards, and Nelsen Middle School Improvements Preliminary Geotechnical Engineering Report Renton, Washington Preliminary Design Recommendations • III. PRELIMINARY DESIGN RECOMMENDATIONS 8.0 INTRODUCTION Our exploration indicates that, from a geotechnical standpoint, the proposed project is feasible provided the recommendations contained herein are properly followed. The existing fill soils are adequate for pavement and new athletic field subgrade support, provided they can be recompacted to a firm, non-yielding condition and are not highly organic. Existing fill is not suitable for support of new foundations; structural fill or native glacial deposits are suitable for support of shallow foundations with proper preparation. The bearing stratum for structures is highly variable. We should be allowed to review project plans as they develop to provide case- by-case recommendations for foundation support of new structures, as needed. The site soils are generally not conducive to infiltration of storm water, as storm water will tend to perch above the existing soils. If permeable pavement is still being considered for this project, adequate storage of infiltrating storm water will need to be incorporated into the pavement sections. In addition, provisions to collect and dispose of the storm water runoff in excess of the permeable pavement storage and infiltration capacity will be necessary. 9.0 SITE PREPARATION Site preparation of foundation, playfield, and pavement areas should include removal of all grass, trees, brush, asphalt, debris, and any other deleterious materials. Any depressions below planned final grades caused by demolition activities should be backfilled with structural fill, as discussed under the "Structural Fill" section. Fill within the existing areas to receive new pavement or athletic field fill may be left in place provided it is inorganic, and can be compacted to a firm, non-yielding condition. It should be understood that placing new fill over the existing fill may result in settlement of pavement or structures planned for this site requiring periodic maintenance. If settlement-sensitive improvements, such as synthetic sports fields, concession stands, or bleachers are planned in areas of existing fill, we should be allowed to offer situation-specific recommendations. In such situations, the District must make decisions to balance costs of removing existing fill versus risks of post-construction settlement. We are available to answer questions during the decision process. The actual observed in-place depths of fill at the exploration locations are presented on Figure 2 and the exploration logs in the Appendix. All soils disturbed by stripping and grubbing operations should be recompacted as described below for structural fill. Once excavation to subgrade elevation is complete, the resulting surface should be proof-rolled with a loaded dump truck or other suitable equipment or systematically probed with a '/z-inch-diameter steel probe under our observation. Any soft, loose, or yielding areas should May 16, 2011 ASSOCIATED EARTH SCIENCES, INC. JPL.hb/ld-KEII0083A3-Projecrs120I100831KEIWP Page 14 Subsurface Exploration, Geologic Hazards, and Nelsen Middle School Improvements Preliminary Geotechnical Engineering Report • Renton, Washington Preliminary Design Recommendations be excavated to expose suitable bearing soils. The subgrade should then be compacted to at least 90 percent of the modified Proctor maximum dry density, as determined by the ASTM:D-1557 test procedure, and to a firm, non-yielding condition. Structural fill can then be placed to achieve desired grades, where needed and approved. 9.1 Temporary Cut Slopes In our opinion, stable construction slopes should be the responsibility of the contractor and should be determined during construction. For estimating purposes, however, temporary unsupported cut slopes can be planned at 1H:1V (Horizontal:Vertical) or flatter in the glacial drift deposits and 1.5H:1V in existing fill soils provided they are not saturated. Permanent cut or fill slopes should not be steeper than 21-1:1V. These slope angles are for areas where ground water seepage is not encountered, and assume that surface water is not allowed to flow across the temporary slope faces. If ground or surface water is present when the temporary excavation slopes are exposed, flatter slope angles will be required. As is typical with earthwork operations, some sloughing and raveling may occur, and cut slopes may have to be adjusted in the field. In addition, WISHA/OSHA regulations should be followed at all times. 9.2 Site Disturbance Most of the on-site soils contain substantial fine-grained material, which makes them moisture- sensitive and subject to disturbance when wet. The contractor must use care during site preparation and excavation operations so that the underlying soils are not softened. If disturbance occurs, the softened soils should be removed and the area brought to grade with structural fill. 9.3 Winter Construction Due to the moderate to high in situ moisture content of most of the site soils as judged in the field and confirmed through laboratory testing, it will likely be necessary to dry some of the site soils during favorable dry weather conditions to allow reuse in structural fill applications. Reuse of excavated site soils in compacted structural fill applications is only acceptable if such reuse is explicitly allowed by project plans and specifications. If construction takes place in winter, drying is not expected to be feasible, and we anticipate that some of the glacial drift soils and existing fill will be unsuitable for structural fill applications. Even during dry weather, site soils excavated for installation of buried utilities might not be suitable for utility backfill under paving or other structures. We recommend budgeting for backfill of buried utility trenches in structural areas with imported select structural fill. For summer construction, significant but unavoidable effort may be needed to scarify, aerate, and dry site soils that are above optimum moisture content to reduce moisture content prior to compaction in structural fill applications. Care should be taken to seal all earthwork areas during mass May 16, 2011 ASSOCIATED EARTH SCIENCES, INC. JPL/h/rd-KE110083A3-Projects 1201/00831KEI WP Page 15 Subsurface Exploration, Geologic Hazards, and Nelsen Middle School Improvements Preliminary Geotechnical Engineering Report Renton, Washington Preliminary Design Recommendations • grading at the end of each workday by grading all surfaces to drain and sealing them with a smooth-drum roller. Stockpiled soils that will be reused in structural fill applications should be covered whenever rain is possible. If winter construction is desired and approved by the City, the existing pavement or new crushed rock fill could be used to provide construction staging areas. The stripped subgrade for crushed rock staging areas should be observed by the geotechnical engineer and should then be covered with a geotextile fabric, such as Mirafi 500X or equivalent. Once the fabric is placed, we recommend using a crushed rock fill layer at least 10 inches thick in areas where construction equipment will be used. 10.0 STRUCTURAL FILL Structural fill may be necessary to establish desired grades in some areas of the site. All references to structural fill in this report refer to subgrade preparation, fill type, placement, and compaction of materials, as discussed in this section. If a percentage of compaction is specified under another section of this report, the value given in that section should be used. After stripping, planned excavation, and any required overexcavation have been performed to the satisfaction of the geotechnical engineer/engineering geologist, the upper 12 inches of exposed ground should be recompacted to 90 percent of ASTM:D-1557. If the subgrade contains too much moisture, adequate recompaction may be difficult or impossible to obtain, and should probably not be attempted. In lieu of recompaction, the area to receive fill should be blanketed with washed rock or quarry spalls to act as a capillary break between the new fill and the wet subgrade. Where the exposed ground remains soft and further overexcavation is impractical, placement of an engineering stabilization fabric may be necessary to prevent contamination of the free-draining layer by silt migration from below. After recompaction of the exposed ground is tested and approved, or a free-draining rock course is laid, structural fill may be placed to attain desired grades. Structural fill is defined as non-organic soil, acceptable to the geotechnical engineer, placed in maximum 8-inch loose lifts with each lift being compacted to 95 percent of ASTM:D-1557. In the case of roadway and utility trench filling, the backfill should be placed and compacted in accordance with City of Renton codes and standards. The top of the compacted fill should extend horizontally outward a minimum distance of 3 feet beyond the locations of the perimeter footings or roadway edges before sloping down at a maximum angle of 2H:1V. The contractor should note that any proposed fill soils must be evaluated by AESI prior to their use in fills. This would require that we have a sample of the material at least 72 hours in advance to perform a Proctor test and determine its field compaction standard. Soils in which the amount of fine-grained material (smaller than the No. 200 sieve) is greater than approximately 5 percent (measured on the minus No. 4 sieve size) should be considered May 16, 2011 ASSOCIATED EARTH SCIENCES, INC. IPL/rb/fd-KE/10083A3-Projecrs120!/00831KE•IWP Page 16 Subsurface Exploration, Geologic Hazards, and Nelsen Middle School Improvements Preliminary Geotechnical Engineering Report • Renton, Washington Preliminary Design Recommendations moisture-sensitive. All of the soil types observed on-site are estimated and have been confirmed by laboratory testing to contain significantly more than 5 percent fine-grained material. Use of moisture-sensitive soil in structural fills should be limited to favorable dry weather and dry subgrade conditions. The on-site soils contain substantial amounts of silt and are considered highly moisture- and disturbance-sensitive when excavated and used as fill materials. At the time of our exploration program, soil moisture content tests indicated that most soils encountered were at moisture conditions very near or above optimum for structural fill use. We anticipate that most excavated soils will require aeration and drying prior to compaction in structural fill applications. Reuse of excavated site soils in structural fill applications is only acceptable if such reuse is specifically allowed by project plans and specifications. If fill is placed during wet weather or if proper compaction cannot be obtained, a select import material consisting of a clean, free-draining gravel and/or sand should be used. Free-draining fill consists of non-organic soil with the amount of fine-grained material limited to 5 percent by weight when measured on the minus No. 4 sieve fraction and at least 25 percent retained on the No. 4 sieve. 11.0 FOUNDATIONS Spread footings may be used for structural support when founded directly on undisturbed glacial deposits or on structural fill placed above suitable native deposits, as previously discussed. We recommend that an allowable bearing pressure of 2,500 pounds per square foot (psf) be used for design purposes, including both dead and live loads. An increase of one-third may be used for short-term wind or seismic loading. Higher foundation soil bearing pressures are possible for foundations supported entirely on undisturbed glacial drift deposits; however, we do not expect that higher bearing pressures will be needed. If higher foundation soil bearing pressures are needed, we should be allowed to offer situation-specific recommendations. Perimeter footings should be buried at least 18 inches into the surrounding soil for frost protection. However, all footings must penetrate to the prescribed bearing stratum, and no footing should be founded in or above organic or loose soils. All footings should have a minimum width of 18 inches. It should be noted that the area bound by lines extending downward at 1H:1V from any footing must not intersect another footing or intersect a filled area that has not been compacted to at least 95 percent of ASTM:D-1557. In addition, a 1.5H:1V line extending down from any footing must not daylight because sloughing or raveling may eventually undermine the footing. Thus, footings should not be placed near the edge of steps or cuts in the bearing soils. May 16, 2011 ASSOCIATED EARTH SCIENCES, INC. JPL/ib/Id-KE!10083A3-Projects1201100831KEIWP Page 17 Subsurface Exploration, Geologic Hazards, and • Nelsen Middle School Improvements Prelitninaiy Geotechnical Engineering Report Renton, Washington Preliminary Design Recontntendations • Anticipated settlement of footings founded as described above should be on the order of 3/4 inch or less. However, disturbed soil not removed from footing excavations prior to footing placement could result in increased settlements. All footing areas should be inspected by AESI prior to placing concrete to verify that the design bearing capacity of the soils has been attained and that construction conforms to the recommendations contained in this report. Such inspections may be required by the governing municipality. Perimeter footing drains should be provided, as discussed under the "Drainage Considerations" section of this report. If new foundations are planned in areas of existing fill, we should be allowed to offer situation- specific recommendations. Solutions might include removing existing fill, constructing rock- filled trenches, limited overexcavation and replacement of existing fill, or other alternatives. 11.1 Drainage Considerations Foundations should be provided with foundation drains placed at the base of footing elevation. Drains should consist of rigid, perforated, polyvinyl chloride (PVC) pipe surrounded by washed pea gravel. The drains should be constructed with sufficient gradient to allow gravity discharge away from the proposed structures. Roof and surface runoff should not discharge into the footing drain system, but should be handled by a separate, rigid, tightline drain. In planning, exterior grades adjacent to walls should be sloped downward away from the proposed structures to achieve surface drainage. 12.0 FLOOR SUPPORT Floor slabs can be supported on suitable native sediments, or on structural fill placed above suitable native sediments. Floor slabs should be cast atop a minimum of 4 inches of clean, washed, crushed rock (such as 5/8-inch "chip") or pea gravel to act as a capillary break. Areas of subgrade that are disturbed (loosened) during construction should be compacted to a non- yielding condition prior to placement of capillary break material. Floor slabs should also be protected from dampness by an impervious moisture barrier at least 10 mils thick. The moisture barrier should be placed between the capillary break material and the concrete slab. 13.0 FOUNDATION WALLS All backfill behind foundation walls or around foundation units should be placed as per our recommendations for structural fill and as described in this section of the report. Horizontally backfilled walls, which are free to yield laterally at least 0.1 percent of their height, may be designed using an equivalent fluid equal to 35 pounds per cubic foot (pet). Fully restrained, horizontally backfilled, rigid walls that cannot yield should be designed for an equivalent fluid of 50 pcf. Walls with sloping backfill up to a maximum gradient of 2H:1V should be designed using an equivalent fluid of 55 pcf for yielding conditions or 75 pcf for fully restrained May 16, 2011 ASSOCIATED EARTH SCIENCES, INC. JPLdb/rd-KE110083A3-Projects1201100831KEIWP Page 18 Subsurface Exploration, Geologic Hazards, and Nelsen Middle School hnprovements Preliminary Geotechnical Engineering Report Renton, Washington Preliminary Design Recommendations conditions. If parking areas are adjacent to walls, a surcharge equivalent to 2 feet of soil should be added to the wall height in determining lateral design forces. As required by the 2009 IBC, retaining wall design should include a seismic surcharge pressure in addition to the equivalent fluid pressures presented above. Considering the site soils and the recommended wall backfill materials, we recommend a seismic surcharge pressure of 8H and 12H psf, where H is the wall height in feet for the "active" and "at-rest" loading conditions, respectively. The seismic surcharge should be modeled as a rectangular distribution with the resultant applied at the mid-point of the walls. The lateral pressures presented above are based on the conditions of a uniform backfill consisting of excavated on-site soils, or imported structural fill compacted to 90 percent of ASTM:D-1557. A higher degree of compaction is not recommended, as this will increase the pressure acting on the walls. A lower compaction may result in settlement of the slab-on-grade or other structures supported above the walls. Thus, the compaction level is critical and must be tested by our firm during placement. Surcharges from adjacent footings or heavy construction equipment must be added to the above values. Perimeter footing drains should be provided for all retaining walls, as discussed under the "Drainage Considerations" section of this report. It is imperative that proper drainage be provided so that hydrostatic pressures do not develop against the walls. This would involve installation of a minimum, 1-foot-wide blanket drain to within 1 foot of finish grade for the full wall height using imported, washed gravel against the walls. A prefabricated drainage mat is not a suitable substitute for the gravel blanket drain unless all backfill against the wall is free-draining. 13.1 Passive Resistance and Friction Factors Lateral loads can be resisted by friction between the foundation and the natural glacial soils or supporting structural fill soils, and by passive earth pressure acting on the buried portions of the foundations. The foundations must be backfilled with structural fill and compacted to at least 95 percent of the maximum dry density to achieve the passive resistance provided below. We recommend the following allowable design parameters: • Passive equivalent fluid = 250 pcf • Coefficient of friction = 0.30 14.0 ATHLETIC FIELD CONSIDERATIONS We understand that athletic field improvements, consisting of two new baseball fields and a new soccer field, are currently proposed as part of the new improvements project. Existing fill was encountered within the fields with the deepest fills occurring near the northwest corner of May 16, 2011 ASSOCIATED EARTH SCIENCES, INC. JPL/tG/!d-KE110083A3-Projects1201100831KE1WP Page 19 Subsurface Exploration, Geologic Hazards, and Nelsen Middle School Improvements Preliminary Geotechnical Engineering Report Renton, Washington Preliminary Design Recommendations • the subject site. If this fill can be recompacted to a firm, non-yielding condition, it can be used to support the new surfacing. It is unknown at this time if the new surfacing will be natural or synthetic turf. Synthetic turf and natural turf fields that incorporate underdrains are settlement-sensitive structures. Post-construction settlement may render portions of the subdrain system ineffective, and may result in field surfaces with visible low spots. Such settlement effects are difficult and costly to repair, particularly when synthetic turf is used. Considering the substantial depth of existing fill below some portions of the site, complete removal of existing fill is likely not an economically viable alternative. Construction of new settlement-sensitive fields above existing fill carries risks of post-construction settlement. We are available to discuss settlement risks and approaches to reduce those risks when project plans have been formulated. Possible approaches include partial removal and recompaction of existing fill, or selecting athletic field design approaches that are less settlement-sensitive and easier to re- level. 14.1 Subsurface Drains (Underdrains) If athletic field underdrains are planned, the new underdrain system should consist of perforated PVC pipes, a minimum of 4 inches in diameter, placed approximately 15 to 20 feet apart. At this site, it might be appropriate to use steeper gradients than normal or underdrain system pipes to allow them to maintain flow if higher than normal post-construction settlement occurs. The pipes should have an invert of at least 12 inches below grade and be fully enveloped in at least 6 inches of free-draining material, containing less than 3 percent fines. The diameter of the drainage material should be larger than the size of the perforations in the drainpipe. The remainder of the drainage trench backfill should consist of free-draining material, conforming to the 2002 Washington State Department of Transportation (WSDOT) Standard Specifications for Road, Bridge and Municipal Construction, Section 9-03.12(4) "Gravel Backfill for Drains," which freely communicates with the field surfacing. We defer to the athletic field designer for specification of the new fields' surfacing material. 14.2 Subsurface Drain Trenching Construction of the subsurface drains will require trenching into the underlying sediments. As part of this study, borings were advanced within the athletic fields to provide preliminary information on sediment density and ease of trenching. The fill soils within the athletic fields are in a loose to medium dense condition and should therefore be backhoe-excavated with limited difficulty. The underlying natural sediments consist of glacial drift soils, which are in a dense to very dense condition. The drift will be more difficult to excavate than the overlying fill soils, particularly where gravels and cobbles are present. Therefore, the contractor should be prepared to encounter dense to very dense sediments during the construction of the subsurface drains, and suitable excavation equipment should be utilized to expedite construction. May 16, 2011 ASSOCIATED EARTH SCIENCES, INC. JPLkb/Id-KE110083A3-Projeus1201100831KEIWP Page 20 Subsurface Exploration, Geologic Hazards, and Nelsen Middle School Improvements Preliminary Geotechnical Engineering Report • Renton, Washington Preliminary Design Recommendations 14.3 Light Pole Foundations We are unaware at this point if new field lighting will be constructed as part of the field improvements. We offer the following recommendations to be used if new light poles are planned. Compressive Capacities We recommend that drilled pier(s) be used for light pole foundations. Where feasible, the piers should penetrate at least 5 feet into very dense glacial drift soils. For vertical compressive soil bearing values, we recommend using a unit end-bearing capacity of 5 tons per square foot (tsf) for glacially consolidated sediments. If light poles must be constructed in areas of existing fill deeper than light pole foundations, end bearing should be neglected in the structural design. The allowable end-bearing capacity includes a safety factor of 2.0 or more. Frictional Resistance For frictional resistance along the shaft of the drilled pier, acting both in compression and in uplift, allowable skin friction values of 1,000 psf in glacially consolidated sediments, and 250 psf in fill soils are recommended. It is also recommended that frictional resistance be neglected in the uppermost 2 feet below the ground surface. The allowable skin friction value includes a safety factor of at least 2.0. Lateral Capacities For design against lateral forces on the drilled pier, two methods are typically used. The parameter used to select the most appropriate design method is the length to pier stiffness factor ratio L/T, where "L" is the pier length in inches and "T" is the relative stiffness factor. The relative stiffness factor for the pier (T) should be computed by: T = SJ EI nll where: E = modulus of elasticity (pounds per square inch [psi]) I = moment of inertia (in') nh = constant of horizontal subgrade reaction (pounds per cubic inch [pci]) The factors "E" and "I" are governed by the internal material strength characteristics of the pier. Representative values of "nn" for the soil observed on this site are presented subsequently. Piers with a L/T ratio of less than 3 may be assumed to be relatively rigid and act as a pole. The passive pressure approach may be used for this condition. For piers with a May 16, 2011 ASSOCIATED EARTH SCIENCES, INC. JPL/tb/ld-KE110083A3-Projects1201100831KE1WP Page 21 Subsurface Exploration, Geologic Hazards, and Nelsen Middle School Improvements Preliminary Geotechnical Engineering Report Renton, Washington Preliminary Design Recommendations L/T ratio greater than 3, the modulus of subgrade reaction method is typically used. Both of these methods are discussed below. Modulus of Subgrade Reaction Method Using this method, the pier is designed to resist lateral loads based on acceptable lateral deflection limits. For granular soils, the coefficient of horizontal subgrade reaction is considered to increase linearly with depth along the pier. The expression for the soil modulus "Kh" is Kh = (nh)(X/B), where "nh" is the coefficient of modulus variation, "X" is the depth below the ground surface, and "B" is the pier diameter. We recommend using the value for the coefficient of modulus variation (nh) of 150 pci for very dense glacial soils and 30 pci for existing fill soils. Passive Pressure Method Lateral loads on the shallow foundation caused by seismic or transient loading conditions may be resisted by passive soil pressure against the side of the foundation. An allowable passive earth pressure of 350 pounds per cubic foot (pcf), expressed as an equivalent fluid unit weight, may be used for that portion of the foundation embedded within dense to very dense native drift. Below a depth of 2 feet in existing loose to medium dense fill soils, an allowable passive earth pressure of 200 pcf should be used. The above value only applies to foundation elements cast "neat" against undisturbed soil. For new structural fill placed around the pier shaft, a passive earth pressure value of 250 pcf is recommended. All fill must be placed as structural fill and compacted to at least 95 percent of ASTM:D-1557. Passive resistance within the upper 2 feet should be ignored. However, passive values presented are used assuming an equivalent triangular fluid pressure distribution over 2 pier diameters beginning at the surface and held at a constant depth greater than 8 feet. The triangular pressure distribution is truncated above 2 feet. The presence of large-diameter boulders below the proposed light pole locations is possible. The owner should be prepared to move the light pole locations if boulders are encountered. Some drilling contractors can employ specialized drilling equipment to drill through large boulders, but these methods are often very time consuming and/or expensive. 15.0 PAVEMENT RECOMMENDATIONS We understand that permeable pavement is being considered for the parking area to the west of the existing building, and that new conventional pavement may also be included with the proposed improvements. We have presented recommendations for new conventional pavement and porous pavement in the sections that follow. May 16, 2011 ASSOCIATED EARTH SCIENCES, INC. JPL/rb/ld-KE11008343-Projects1201100831KEIWP Page 22 Subsurface Exploration, Geologic Hazards, and Nelsen Middle School Improvements Preliminary Geotechnical Engineering Report • Renton, Washington Preliminary Design Recommendations 15.1 New Conventional Pavement Conventional pavement for this project would be supported by very dense silty sand (drift), new structural fill, or recompacted existing fill. These soils should be suitable, with proper preparation, to allow the use of standard paving sections. Because some of the site soils were substantially above optimum moisture content at the time of our exploration program, remedial subgrade preparation might be required below the paving, particularly in areas of existing fill and silty weathered drift soils. Remedial preparation measures could include removal of some of the existing site soils below the planned pavement section and restoring the planned subgrade elevation with select imported structural fill, or aeration and drying of existing soils prior to compaction of the road subgrades. It may be necessary to use a separation fabric between the existing subgrade and new structural fill if fine-grained sediments are exposed during grading. Preparation of pavement subgrade areas should follow the recommendations of the "Site Preparation" and "Structural Fill" sections of this report. The proposed subgrade, whether it is cut native soils or compacted structural fill, should have a minimum density of 95 percent based on the ASTM:D-1557 test procedure within the upper foot below the pavement section. Subsequent to compaction or recompaction, the subgrade should be proof-rolled with a loaded dump truck. Any deflecting areas or soft spots detected during proof-rolling should be excavated and replaced with properly compacted structural fill. We recommend that the final determination of how to prepare the pavement subgrades be made at the time of construction when weather and field conditions are known. Upon completion of any recompaction and proof-rolling, a conventional pavement section consisting of 21/2 inches of asphaltic concrete pavement (ACP) underlain by 4 inches of 11/4-inch crushed surfacing base course is recommended for car parking areas. A heavier section consisting of 3 inches of ACP over 6 inches of crushed rock should be used in areas where bus traffic or other heavy vehicles are expected. The upper 1 inch of 11/4-inch crushed rock can be replaced with 11/2 inches of 5/8-inch crushed rock as a leveling course, if desired. The crushed rock course must be compacted to at least 95 percent of the maximum density. 15.2 Porous Asphalt or Permeable Pavement Recommendations provided for use in planning and design of the porous pavement proposed as surfacing in the area of existing parking area west of the existing building focus on providing a uniform base for support of the porous pavement and allowing maximum infiltration within the soils beneath the pavement. Approximately 10 feet of fill was encountered over glacially consolidated drift in exploration boring EB-13 (Figure 2). The density of the fill within 18 inches of the existing parking lot surface is considered to be predominantly medium dense. In order to provide a uniform base for support of the porous pavement and to allow maximum infiltration within the soils beneath the pavement, our recommendations include scarification of the upper 12 inches of soil and all across the exposed parking subgrade. May 16, 2011 ASSOCIATED EARTH SCIENCES, INC, !PL/tb/ld-KEIIO083A3-Projects120110083IKEIWP Page 23 Subsurface Exploration, Geologic Hazards, and Nelsen Middle School Improvements Preliminary Geotechnical Engineering Report Renton, Washington Preliminary Design Recommendations • The surface of the parking lot should then be graded to drain at a gradient of no more than 1 percent toward the present surface water drainage system. Soil removal and surface grading should be done in such a way as to avoid densification of the exposed soil surface. Following subgrade preparation, we recommend a passenger car pavement section consisting of a 3-inch compacted porous asphalt paving above a 3-inch thickness of "choker course" consisting of 5/8-inch crushed surfacing top course. Below the choker course, a 12- to 18-inch- thick storage layer consisting of 2-inch permeable ballast (WSDOT 9-03.9[2]) should be placed above the soil subgrade. The storage layer should be sized for an appropriate amount of storm water storage assuming a porosity of 0.30. Since a limited amount of the water will infiltrate the pavement subgrade during large storm events, a drainage system should be established on the downgradient side(s) of the permeable pavement. The drainage system should include perforated pipes connected to the site storm drain system. In areas where buses, garbage trucks, fire trucks, delivery trucks, or other heavy vehicles will be driven or parked, we recommend a paving section consisting of 6 inches of porous asphalt, 3 inches of choker course, and 18 inches of storage layer. Porous asphalt requires regular cleaning to avoid becoming clogged with silt and contaminants and to maintain the porous properties. We recommend the RSD establish a cleaning schedule as part of the long-term site maintenance. 16.0 DETENTION POND CONSIDERATIONS We understand that a detention pond is currently under consideration at the northwest portion of the subject site as part of the proposed improvements. As part of our exploration program, we completed three exploration borings at the area of the proposed northwestern detention pond. In summary, these exploration borings encountered loose to medium dense fill to depths ranging up to 31 feet, with the deeper fill encountered near to the top of the steep slope leading downward to the west of the subject site. Since fill sediments were encountered at the likely elevations of the pond bottom and side slopes, it is our opinion that the pond needs to be provided with a liner. A synthetic liner is recommended over a soil liner for this project because future settlement in the underlying fill may lead to "cracking" and leaks in a soil liner, which may adversely impact the nearby steep slope. We have also included recommendations for the use of a cellular confinement system to retain the pond liner cover soil or topsoil growth medium above the liner, if required. Since the pond will be lined, the existing fill can remain in place, provided the material is cleaned of debris, moisture-conditioned, and compacted to a firm and unyielding condition. A cellular confinement system is recommended to retain liner cover soils and any recommended topsoil growth medium above the completed liner. A cellular confinement system, such as Geoweb° or Terracell®, can be installed for purposes of topsoil containment and slope erosion control. The proposed system should be approved by the geotechnical May 16, 2011 ASSOCIATED EARTH SCIENCES, INC. JPLJrb/ld-KE110083A3-Projects1201100831KE1WP Page 24 Subsurface Exploration, Geologic Hazards, and Nelsen Middle School Improvements Preliminary Geotechnical Engineering Report • Renton, Washington Preliminary Design Recommendations engineer prior to installation. We recommend the use of 6-inch-deep cells. Install the selected system in accordance with the manufacturer's recommendations. Anchors for the cellular confinement system should be installed so as to prevent stress points from forming and to prevent the system from sliding. Anchors should not penetrate the pond liner. The cell openings should be filled with either a clean pit run sand and gravel as a liner cover or topsoil specified by the project landscape architect, depending on location in the pond. Interior detention pond slopes should be made at a maximum gradient of 3H:1V or flatter, and should be consistent with the manufacturer's recommendations for the cellular confinement system that is selected. Exterior perimeter berm slopes, if required, should be made at a maximum gradient of 2H:I V. Perimeter pond berms should have a minimum top width of 6 feet. A base key equal to one-half the berm width and a minimum of 3 feet deep should extend below the base of the pond berm. Additionally, detention pond berm geometry should conform to municipal design standards. AESI is available to perform a geotechnical review of the final detention pond plans once they are available. 17.0 PROJECT DESIGN AND CONSTRUCTION MONITORING At the time of this report, site plans, grading plans, structural plans, and construction methods have not been finalized. We are available to provide additional geotechnical consultation as the project design develops and possibly changes from that upon which this report is based. We recommend that AESI perform a geotechnical review of the plans prior to final design completion. In this way, our earthwork and foundation recommendations may be properly interpreted and implemented in the design. We are also available to provide geotechnical engineering and monitoring services during construction. The integrity of the foundations for buildings and of new pavement depends on proper site preparation and construction procedures. In addition, engineering decisions may have to be made in the field in the event that variations in subsurface conditions become apparent. Construction monitoring services are not part of the current scope of work. If these services are desired, please let us know, and we will prepare a cost proposal. May 16, 2011 ASSOCIATED EARTH SCIENCES, INC. IPL/tb/Id-KE11008343-Projects1201100831KElWP Page 25 Subsurface Exploration, Geologic Hazards, and Nelsen Middle School Improvements Preliminary Geotechnical Engineering Report Renton, Washington Preliminary Design Recommendations We have enjoyed working with you on this study and are confident that these recommendations will aid in the successful completion of your project. If you should have any questions, or require further assistance, please do not hesitate to call. Sincerely, ASSOCIATED EARTH SCIENCES, INC. Kirkland, Washington 4-7 ° r " A q 23580 $1./t<`, �G/S T E9' Gam Jeffrey P. Laub, L.G., L.E.G. Kurt D. Merriman, P.E. Project Engineering Geologist Principal Engineer Attachments: Figure 1: Vicinity Map Figure 2: Site and Exploration Plan Appendix: Exploration Logs Laboratory Test Results May 16, 2011 ASSOCIATED EARTH SCIENCES, INC. JPL/th/!d-KE110083A3-Projects1201100831KEIWP Page 26 . , , -, ;.,/,./7,- ,, , Slim .4,,, 4— re /, ',--,,,,,'',„„.0,H.A,4, • ,., '-:4,,,t',$ A- i i ,.... 4 ,- -,*.ht 1Y imiqft ( r, , , 4 Viet, '....'''''''''':--,-',,,,g•—• .,,..41.1. ; N. 'N*:, , Far 1.. :',‘,„' ~ _ '4--i* .' / .4 .) �` ''''‘dl 2 k *''''''"' - ' '-'1111111% ,it,4 1111 ''. "1.1.7.* la 4* ' T ..:.,-...t.„,,, -7---,--,z.„„--z-N,:-,-,,r-i.,,,.., ,.„.„; .,,,,,,,,, ,''' ::::_ , mil., over.,..„ 440 — iikrtr.„...,71,4. 41 ),,r_ist4,\Nt, * .g ir Arr ix B jd�1114`4,-.'''"T in ..—...ii ,� s ' 'E4ripii.. 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Ailk.•;,,,) ,,,,,,...da.''. leg!!! t 3/4 ir Ili:V:kl,:A'4.,, ' -—4, . :,./..,,,:).,f" ,,,,Nrilk,,ty‘t.14„.i , .4;,, „,,„,,, ,,,,, , , I . „ ,„1 lor : .".kfitlikr,t., .i; , It s y s i I, ....;61 ,s, ,,,,,,V.fttPtils'I i .i.,404';'''''--.'`., - # stilifia 4,4, i:,.,,,Trir Agizt k & .11 .---,. ir-gli i ,, ; ..,.. - -711 I : '';''' ..6,-;:-.--,-----; ' tif n 0 .' '1?-k ' 4s.„lkilotp,I.Vit r• ,,,,,, ' „, ,., — , .... v. . a fr" &* bP .. tk .�t- � ji [{ _ 1, ! .‘ i i ,. ■II eJ 1 [ s� b r Y � ¢" , Tukwila c iJ 1 I s. „ lig i ,1 . , , ggpp��cc 1� +11,a7 � �ç Y 41, Ui _a s�(.rc Y ` �',. r44 -i---,1N 'i. 4 '^w � C(IRP s t ', ( , •.,.'�.�';." r� yft S"S c 4 JAS . skew "A„a i li ii mit '1 71::',: , II i+w� /., _milli., Ii.fi:_�. . �S Le o zona ,. ?^err (-� / k n REFERENCE: USGS TOPO! FEET Associated Earth Sciences, Inc. VICINITY MAP FIGURE 1 Z NELSEN MIDDLE SCHOL DATE 4/11 :' '011 RENTON, WASHINGTON PROJ.NO. KE1100&3A • EE � ' EB-8 31' E : ' EB-7 13' •E - ,p M W- EB-6 1 ELS-1 a 0 EB-11 EB-13 1�= 1 , pi g'4,7‘., ,,.,r 1 EB-12 �„ A 'PR IIA E LOCATION CSF E FL A'I"IO L GRIN+G WITH AF ) DH E E S I`I d IPFRATE L b `I411EPTW'INQICATESO MOM IORIN WI'.AI L. TYP J I. fp„.-.', ,...i% "*631 7..,11, ;,, , ' i ,�� . :.: ., " NAS -,K .,,',..,4ii,. t,,,.....' ,,,,,,I.,...,_ -,,, .,.g.,-, ,..., , , ., ,,,), . , ..,...,.. . . , , , .,. $ s � : a. 0 100 200a ait , . �; ci REFERENCE: KING COUNTY GIS FEET w Associated Earth Sciences, Inc. SITE AND EXPLORATION PLAN FIGURE 2 Z re I FrfNELSEN MIDDLE SCHOOL DATE 5111 i RENTON, WASHINGTON PROJ.NO. KE110083A APPENDIX 0 0 0 0 0 Well-graded gravel and Terms Describing Relative Density and Consistency v . O .r m "'y o°g°,GW gravel with sand,little to Density SPT(2)blows/foot a �; Associated Earth Sciences,Inc. Exploration Log 4\71c �: Project Number Exploration Number Sheet v 1 .., KE110083A EB-1 1 of 1 Project Name Nelsen Middle School Ground Surface Elevation(ft) Location Renton, WA Datum N/A Driller/Equipment Boretec/Track Rig Date Start/Finish 4/18/11,4/18/11 Hammer Weight/Drop 140#/30" Hole Diameter(in) 11' c U— U > ` Co E =a> - Blows/Foot n s E `` >. o a� o T cin C9 rn U m m .c DESCRIPTION ° 10 20 30 40 ° Undifferentiated Stratified Drift I S-1 Moist,brownish gray,silty fine SAND,with gravel. 37 90/4" 50/e" — 5 I S-2 Moist,slightly rust-stained brownish gray,silty fine to medium SAND,with 508„ X50/2" gravel. I S-3 Moist,brownish gray,silty fine to medium SAND,with gravel and brown 32 sand pockets. 50/4" 5014" — 10Moist,brownish gray,silty fine to medium SAND,with gravel. 6X50/5" I S-4 50/E" Bottom of exploration boring at 10 9 feet — 15 — 20 — 25 0 - N N N C n Q' a c7 a Sampler Type(ST): II 2"OD Split Spoon Sampler(SPT) [ No Recovery M-Moisture Logged by: ,1PL o m 3"OD Split Spoon Sampler(D&M) U Ring Sample Water Level() Approved by: m ,, Grab Sample Shelby Tube Sample 1 Water Level at time of drilling(ATD) Associated Earth Sciences, Inc. Exploration Log Project Number Exploration Number Sheet KE110083A EB-2 1 of 1 Project Name Nelsen Middle School Ground Surface Elevation(ft) Location Renton, WA Datum N/A Driller/Equipment Boretec/Track Rig Date StarUFinish 4/18/11,4/18/11 Hammer Weight/Drop 140#/30" Hole Diameter(in) A" c m w U U— O > U' O L —_1 J N Blows/Foot c S E m E o o T 0° o m DESCRIPTION ° 10 20 30 40 ° Undifferentiated Stratified Drift Moist,slightly rust-stained brownish gray,silty fine to medium SAND,with S-1 gravel 11 A34 23 5 Moist, brownish gray,silty fine SAND,with gravel 15 S-2 33 £80 47 I S-3 Moist,same_ 33 50/E" £50/6" – 10 Moist,brownish gray,silty fine to medium SAND,with gravel. S-4 23 28 £76 48 – 15 — Moist,brown,fine to medium SAND,with gravel and trace silt. S-5 26 _ 29 £62 33 Bottom of exploration boring at 16 5 feet — 20 — 25 Q CL' c7 Sampler Type(ST). 2"OD Split Spoon Sampler(SPT) El No Recovery M-Moisture Logged by: JPL o al 3"OD Split Spoon Sampler(D&M) a Ring Sample Q Water Level 0 Approved by: wGrab Sample Shelby Tube Sample 1 Water Level at time of drilling(ATD) Associated Earth Sciences,Inc. Exploration Log Project Number Exploration Number Sheet KE 110083A EB-3 1 of 1 Project Name Nelsen Middle School Ground Surface Elevation(ft) Location Renton, WA Datum N/A Driller/Equipment Boretec/Track Rig Date Start/Finish 4/1R/11 4/18/11 Hammer Weight/Drop 140#/30" Hole Diameter(in) 6' c r o o > m rn N Blows/Foot S E E E, � ) o u) m -c c.)T �' C9 DESCRIPTION m 10 20 30 40 Fill 6 inches wet,brown,silty SAND,with gravel and organics over moist, 5 S-6 bluish gray,silty SAND,with gravel 8 A. 9 – 5 Moist,brownish gray and bluish gray,silty SAND,with gravel. 9 S-7 11 £22 ii Moist,same. S-8 4 A 3 – 10 — Moist to wet,brown and gray,silty SAND,with gravel and organics3. S-9 3 A6 3 Undifferentiated Stratified Drift -- 15 Moist,rust-stained gray,silty fine to medium SAND,with gravel S-10 g A22 13 Weathered Tertiary Bedrock – 20 Moist,brownish gray,silty fine SAND,with gravel. J F 0/ „ I S-1 1 A50/9" Bottom of exploration boring at 20 4 feet - 25 Q Q a C7 a Sampler Type(ST): 2"OD Split Spoon Sampler(SPT) J No Recovery M-Moisture Logged by: JPL lin 3"OD Split Spoon Sampler(D&M) II Ring Sample Q Water Level 0Approved by: Grab Sample 0 Shelby Tube Sample T. Water Level at time of drilling (ATD) • Associated Earth Sciences,Inc. Exploration Log Project Number Exploration Number Sheet KE110083A EB-4 1 of 1 Project Name Nelsen Middle School Ground Surface Elevation(ft) Location Renton, WA Datum NIA Driller/Equipment Boretec/Track Rig Date Start/Finish 4/18/1 1 4/1 8/1 1 Hammer Weight/Drop 140#/30" Hole Diameter(in) 6" c a� co N L o N ( -ail) -I Blows/Foot S > 0 E o T c`n v7 o io m DESCRIPTION o 10 20 30 40 ° Fill Moist,brown,silty SAND,with gravel and organics 3 S-1 7 A13 6 – 5 — Moist to wet,brown and gray,silty SAND,with gravel and organics. S-2 b Ag 3 Moist,rust-stained gray,silty fine to medium SAND,with gravel. 4 S-3 8 A21 13 Undifferentiated Stratified Drift – 10 Moist,brownish gray,silty fine SAND,with gravel S-4 20 £55 35 15 Moist,with rust staining,same– 50IE" I S-5 A50/8" Bottom of exploration boring at 15.5 feet – 20 – 25 0 N a a Sampler Type(ST): 2"OD Split Spoon Sampler(SPT) J No Recovery M-Moisture Logged by: JPL o m 3"OD Split Spoon Sampler(D&M) El Ring Sample Q Water Level 0 Approved by: CD Grab Sample Q Shelby Tube Sample 1 Water Level at time of drilling(ATD) Associated Earth Sciences,Inc. Exploration Log Project Number Exploration Number Sheet • - KE110083A EB-5 1 of 1 Project Name Nelsen Middle School Ground Surface Elevation(ft) Location Renton, WA Datum N/A Driller/Equipment Boretec/Track Rig Date Start/Finish 4/18/11 4/18/11 Hammer Weight/Drop 140#/ 30" Hole Diameter(in) A" c a> Y U— 0 > ' — J Blows/Foot a S E a) t° E o a� T `7) ° DESCRIPTION ° m 10 20 30 40 ° Undifferentiated Stratified Drift Moist,slightly rust-stained,silty fine to medium SAND,with gravel. 19 S-1 26 £53 27 - 5 Moist,brownish gray,silty fine to medium SAND,with gravel and sand S-2 lenses. 17g A4= 22 Moist,brownish gray,fine to medium SAND,with gravel. 9 S-3 16 A38 22 — 10 Moist,same S-4 158 A59 31 — 15 Moist,same. S-5 202 41,50 28 Bottom of exploration boring at 16 5 feet — 20 — 25 0 8. a 0 Sampler Type(ST): C 2"OD Split Spoon Sampler(SPT) [ No Recovery M-Moisture Logged by: JPL o [r 3"OD Split Spoon Sampler(D&M) [ Ring Sample Water Level() Approved by: �' Water Level at time of drilling(ATD) N Grab Sample 0 Shelby Tube Sample T. Associated Earth Sciences,Inc. Exploration Log Project Number Exploration Number Sheet - KE110083A EB-6 1 of 1 Project Name Nelsen Middle School Ground Surface Elevation(ft) Location Renton,WA Datum N/A Driller/Equipment Boretec/Track Rig Date Start/Finish 4/18/11,4118/11 Hammer Weight/Drop 140#130" Hole Diameter(in) 6° c a. cn L O > _ cu (D cuN =11J N Blows/Foot S �E ° T `� (-9(i) DESCRIPTION ° m 10 20 30 40 ° Fill Moist to wet,rust-stained brown,silty SAND,with gravel. 16 S-1 24 A39 15 — 5 Moist to wet,same with woody debris. S-2 5 A 12 6 Wet,same S-3 4 Ag 5 — 10 Moist,rust-stained brownish gray,silty SAND,with gravel 5 S-411 A24 13 — 15 — Moist to wet,brown and gray,silty SAND,with gravel and organics7. S-5 8 A23 15 — 20 Moist,same. S-6 6 ♦1 E. 9 — 25 — Same for 6 inches. Undifferentiated Stratified Drift S-7 Moist,slightly rust-stained,silty fine to medium SAND,with gravel 20 £51 31 Bottom of exploration boring at 26.5 feet a Sampler Type(ST): C 2"OD Split Spoon Sampler(SPT) No Recovery M-Moisture Logged by: JPL m 3"OD Split Spoon Sampler(D&M) U Ring Sample SZ Water Level 0Approved by: CO Grab Sample 0 Shelby Tube Sample 3--t Water Level at time of drilling(ATD) Associated Earth Sciences,Inc. Exploration Log Project Number Exploration Number Sheet KE110083A EB-7 1 of 1 Project Name Nelsen Middle School Ground Surface Elevation(ft) Location Renton, WA Datum N/A Driller/Equipment Boretec/Track Rig Date Start/Finish 4/18/11 4/1R/11 Hammer Weight/Drop 140#/30" Hole Diameter(in) R" c a� Y U— O > to > °' L �, to Blows/Foot n E `0 T ,a � E o a`> m m 00n m T cc/3 " com 10 20 30 40 ° Fill Moist,rust-stained brownish gray,silty fine to medium SAND,with gravel. S-1 8 A23 18 - 5 Moist to wet,brown and gray,silty fine to medium SAND,with gravel and S-2 organics. g A14 6 Moist to wet,same. S-3 4 Ag 5 — 10 — Undifferentiated Stratified Drift Moist,bluish gray,silty fine to medium SAND. S-A 6 A13 7 — 15 — Moist to wet,rust-stained bluish gray,fine to medium SAND,with silt and S-5 trace gravel. 12 X35 18 Bottom of exploration boring at 16 5 feet — 20 — 25 N (N - a Sampler Type(ST). I 2"OD Split Spoon Sampler(SPT) [ No Recovery M-Moisture Logged by: JPL o m 3"OD Split Spoon Sampler(D&M) U Ring Sample Q Water Level 0Approved by: UJ E Grab Sample ri Shelby Tube Sample[ Water Level at time of drilling(ATD) Associated Earth Sciences, Inc. Exploration Log Project Number Exploration Number Sheet KE110083A EB-8 1 of 2 Project Name Nelsen Middle School Ground Surface Elevation(ft) Location Renton, WA Datum N/A Driller/Equipment Boretec/Track Rig Date Start/Finish 411R/11,4/111/11 Hammer Weight/Drop 140#/ 30" Hole Diameter(in) 6" N U O > w N r co Q a E j L J Blows/Foot m S cEo 0 rtim DESCRIPTION ° 10 20 30 40 ° Fill Moist to wet,brownish gray,silty SAND,with gravel and organics. 6 S-1 15 A30 15 - 5 Moist to wet,same S-2 4 ♦g 4 Wet,rust-stained brownish gray,silty fine to medium SAND,with gravel. 3 S-3 3 A9 6 - 10 Wet,rust-stained brown and gray,silty fine to medium SAND,with gravel S-4 4 A- 3 - 15 — Moist,bluish gray and brown,silty SAND,with gravel and organics. 4 S-5 10 A20 10 - 20 Moist,slightly rust-stained brownish gray,silty fine SAND,with gravel. 12 S-6 13 A25 12 - 25 — Wet,very little recovery,same 13 S-718 A34 16 0 N N - Sampler Type(ST). m 2"OD Split Spoon Sampler(SPT) LI No Recovery M-Moisture Logged by: JPL 3"OD Split Spoon Sampler(D&M) U Ring Sample .V Water Level() Approved by: w ff Grab Sample Shelby Tube Sample i Water Level at time of drilling(ATD) Associated Earth Sciences, Inc. Exploration Log • Project Number Exploration Number Sheet KE110083A EB-8 2 of 2 Project Name Nelsen Middle School Ground Surface Elevation(ft) Location Renton, WA Datum N/A Driller/Equipment Boretec/Track Rig Date Start/Finish 4/1R/11,4/1R/11 Hammer Weight/Drop 140#/30" Hole Diameter(in) R" c a� - N U— o > N L N N —_� -I N Blows/Foot a S E ma n o a) m C5� o o m T c`/13 (i) m 10 20 30 40 ° Stuffed sampler with moist,dark brown,silty SAND,with organics S-8 (slough?). 19 35 A71 Undifferentiated Stratified Drift 36 "Bottom 8 inches moist,gray,fine to medium SAND,with gravel and silt. / Bottom of exploration boring at 31 5 feet — 35 — 40 — 45 — 50 — 55 b Ni N Q n Sampler Type(ST): El 2"OD Split Spoon Sampler(SPT) No Recovery M-Moisture Logged by: JPL m 3"OD Split Spoon Sampler(D&M) II Ring Sample Q Water Level 0Approved by: W ® Grab Sample E Shelby Tube Sample L Water Level at time of drilling(ATD) • Associated Earth Sciences,Inc. Geologic & Monitoring Well Construction Log Project Number Well Number Sheet KE110083A EB-9 1 of 2 Project Name Nelsen Middle School Location Renton, WA Elevation(Top of Well Casing) Surface Elevation(ft) Water Level Elevation Date Start/Finish 4/19/11 4/19/11 Drilling/Equipment Boretec/Track Rig Hole Diameter(in) 6" Hammer Weight/Drop 140#/30" O U OCD 12 >, WELL CONSTRUCTION T m Ci)CD Flush monument Fill \� \� Concrete 0 to 2 feet 4 Moist,brown,silty fine to medium SAND,with gravel and organics. 7 8 — 5 Bentonite chips 2 to 26.5 feet I 3 Moist to wet,same. 3 _T 3 2 Wet,same 2 —10 2-inch PVC casing 0 to 29.5 Moist to wet,rust-stained brown and gray,silty fine to medium feetSAND,with gravel and organics 5 —15 Moist to wet,with woody debris,same 8 - 10 5 Undifferentiated Stratified Drift —20 Moist,slightly rust-stained,silty fine to medium SAND,with gravel. - II1 ,6 32 26 25 I 50 31/4" Moist,brown,fine to coarse SAND,with gravel and silt. N z 10/20 silica sand 26.5 to 39.5 feet o- a Sampler Type(ST): 2"OD Split Spoon Sampler(SPT) Q No Recovery M - Moisture Logged by: JPL m 3"OD Split Spoon Sampler(D&M) U Ring Sample Water Level(4/21/11) Approved by: ® Grab Sample CI Shelby Tube Sample T. Water Level at time of drilling(ATD) Associated Earth Sciences,Inc. Geologic & Monitoring Well Construction Log • Project Number Well Number Sheet KE110083A EB-9 2 of 2 • Project Name Nelsen Middle School Location Renton.WA Elevation(Top of Well Casing) Surface Elevation(ft) Water Level Elevation Date Start/Finish 4/19/11 4/19/11 Drilling/Equipment Boretec/Track Rig Hole Diameter(in) 6" Hammer Weight/Drop 140#/30" > U Q m -' ° E WELL CONSTRUCTION T m CD ci) (i) DESCRIPTION 29 Moist,rust-stained brownish gray,fine to coarse SAND,with gravel. 50/6" 2-inch PVC 0.010"screen 29.5 to 39 5 feet a • —35 34 Wet,brownish gray,fine to coarse SAND,with gravel. 50/6" >,. Screw cap —40 26 Wet,same. 50/5" Boring terminated at 40.9 feet on 4/19/11 —45 — —50 — —55 — N 0 oz Sampler Type(ST). m 2"OD Split Spoon Sampler(SPT) a No Recovery M - Moisture Logged by: JPL 3w m 3"OD Split Spoon Sampler(D&M) U Ring Sample -V Water Level(4/21/11) Approved by: Z ® Grab Sample Shelby Tube Sample t Water Level at time of drilling(ATD) Associated Earth Sciences,Inc. Exploration Log Project Number Exploration Number Sheet KE110083A EB-10 1 of 1 • Project Name Nelsen Middle School Ground Surface Elevation(ft) Location Renton, WA Datum N/A Driller/Equipment Boretec/Track Rig _ Date Start/Finish 4/1 8/1 1 4/18/11 Hammer Weight/Drop 140#/30" Hole Diameter(in) R° > L =a-)15 J N Blows/Foot S Eo a� T rn (-"f) o m DESCRIPTION c.) 10 20 30 40 ° Fill Wet, brown and gray,silty fine SAND,with gravel and organics. 4 S1 10 A28 18 Undifferentiated Stratified Drift — 5 T Moist,slightly rust-stained brownish gray,silty fine SAND,with gravel. 27 S-240 £88 48 Moist,same. S-3 2431 £62 31 — 10 Moist,same. 20 S-4 25 A51 26 Bottom of exploration boring at 11 5 feet — 15 — 20 — 25 • 0 N N (4 a a Sampler Type(ST): _ 2"OD Split Spoon Sampler(SPT) j No Recovery M-Moisture Logged by: JPL 3"OD Split Spoon Sampler(D&M) 11 Ring Sample Q Water Level 0 Approved by: I a• 6 Grab Sample 11 Shelby Tube Sample 1 Water Level at time of drilling (ATD) Associated Earth Sciences,Inc. Exploration Log Project Number Exploration Number Sheet KE110083A EB-11 1 of 1 Project Name Nelsen Middle School Ground Surface Elevation(ft) Location Renton, WA Datum N/A Driller/Equipment Boretec/Track Rig Date Start/Finish 4/19/11,4/1P/11 Hammer Weight/Drop 140#/30" Hole Diameter(in) 6" c a� N w cv 76 .O N i0 fn °' L = N Blows/Foot ~ a S E iP >. a 3 T o cam r DESCRIPTION " 10 20 30 40 ° Fill T Moist to wet,slightly rust-stained brownish gray,silty fine to medium 6 S.1 SAND,with gravel and trace organics. 7 A13 6 - 5 Moist,same. S-2 4 1,9 5 Moist,rust-stained brown and gray,silty fine to medium SAND,with gravel 4 5-3 and trace organics. • 4 S 4 - 10 — Undifferentiated Stratified Drift Moist,rust-stained brownish gray,silty fine to medium SAND,with gravel 2 S-4q Ai; 12 – 15 Moist,slightly rust-stained brownish gray,silty fine to medium SAND,with 5-5 gravel 16 ,, 32 6g 37 Bottom of exploration boring at 16 5 feet – 20 – 25 0 N N N Q Q` E! m a Sampler Type(ST). C 2"OD Split Spoon Sampler(SPT) Q No Recovery M-Moisture Logged by: JPL • m 3"OD Split Spoon Sampler(D&M) El Ring Sample SZ Water Level 0Approved by: • ff Grab Sample Q Shelby Tube Sample 31 Water Level at time of drilling(ATD) • Associated Earth Sciences,Inc. Exploration Log Project Number Exploration Number Sheet . - KE110083A EB-12 1 of 1 • Project Name Nelsen Middle School Ground Surface Elevation(ft) Location Renton, WA Datum N/A Driller/Equipment Boretec/Track Rig Date Start/Finish 4/19/11 4/19/11 Hammer Weight/Drop 140#/30" Hole Diameter(in) R° c a5 u, U- O > ' °' t >T,a� N Blows/Foot T S E >g O O N T DESCRIPTION ° m 10 20 30 40 ° Fill Moist,brown,silty fine to medium SAND,with gravel and organics. S-1 5 AB 4 - 5 Moist,same S-2 g Ats 7 Undifferentiated Stratified Drift Moist,brown,fine to medium SAND,with gravel and sillier zones. S-3 22 22 /4e 23 - 10 — Moist to wet,brownish gray,fine to medium SAND,with trace gravel. S-4 13 A1.7 14 — 15 I Moist,brownish gray,fine to medium SAND,with silt and trace gravel 15 S-5 25 A 48 23 Bottom of exploration boring at 16.5 feet — 20 — 25 0 N N N Q - a c7 _ Q Sampler Type(ST): Oil 2"OD Split Spoon Sampler(SPT) El No Recovery M-Moisture Logged by: JPL 3"OD Split Spoon Sampler(D&M) Ring Sample Q Water Level 0 Approved by: w ® Grab Sample El Shelby Tube Sample 1 Water Level at time of drilling(ATD) Associated Earth Sciences,Inc. Exploration Log • Project Number Exploration Number Sheet ' `' 1 - KE110083A EB-13 1 of 1 Project Name Nelsen Middle School Ground Surface Elevation(ft) Location Renton, WA Datum N/A Driller/Equipment Boretec/Track Rig Date Start/Finish 4/1R/11,4/1R/1 1 Hammer Weight/Drop 140#/30" Hole Diameter(in) 6' Cl) U O O > V) Q S T Q 5 3 Blows/Foot T in (9 o co m DESCRIPTION " 10 20 30 40 ° 4 inches asphalt(two layers),6 inches crushed rock. Fill T Moist,brown,silty SAND,with gravel and asphalt pieces. 18 S-1 17 A35 19 — 5 — Moist,brownish gray,silty fine to medium SAND,with gravel S-2 g A,13 8 Moist,brownish gray,silty fine SAND,with gravel and trace wood debris. 10 S-3 13 •34 . 21 — 10 — Same for 8 inches. Undifferentiated Stratified Drift S-4 Moist,rust-stained brownish gray,silty fine to medium SAND,with trace 13 £32 gravel 19 — 15 S-5 Moist,brownish gray,silty fine SAND,with gravel. 18 - 50/E" 50/6" Bottom of exploration boring at 16 feet — 20 — 25 0 N N N C a - a Sampler Type(ST): W 2"OD Split Spoon Sampler(SPT) Q No Recovery M-Moisture Logged by: JPL I 3"OD Split Spoon Sampler(D&M) [ Ring Sample SZ Water Level() Approved by: .6 Grab Sample Q Shelby Tube Sample 1 Water Level at time of drilling(ATD) • GRAIN SIZE ANALYSIS - MECHANICAL Date Project Project No. Soil Description 04/22/2011 Nelsen Middle School KE110083A Sand little gravel trace silt Tested By Location EB/EP No Depth Intended Use/Specification MS Onsite EB-9 25' Wt.of moisture wet sample+Tare 738.54 Total Sample Tare 335.62 Wt.of moisture dry Sample+Tare 704.83 Total Sample wt +tare 704.83 Wt.of Tare 335.62 Total Sample Wt 369.2 Wt.of moisture Dry Sample 369.21 Total Sample Dry Wt 338.3 Moisture% 9% Specification Requirements Sieve No. Diam. (mm) Wt. Retained (g) % Retained % Passing Minimum Maximum 3 76.1 0.0 100.0 - - 2.5 64 0.0 100.0 - - 2 50.8 0.0 100.0 _ - - 1.5 38.1 0.0 100.0 - - 1 25.4 0.0 100.0 - - 3/4 19 9.43 2.8 97.2 - - 3/8 9.51 38.38 11.3 88.7 - - #4 4.76 79.57 23.5 76.5 - - #8 2.38 118.15 34.9 65.1 - - #10 2 126.97 37.5 62.5 - - #20 0.85 173.08 51.2 48.8 - - #40 0.42 247.63 73.2 26.8 - - _ #60 0.25 299.62 88.6 11.4 - - #100 0.149 318.66 94.2 5.8 - - #200 0.074 330.1 97.6 2.4 - - #270 0.053 335.25 99.1 0.9 - - US STANDARD SIEVE NOS. 3/4" NO 4 NO 16 NO 40 NO 200 100 --0 O O 01a ; I ; i i i I : I ( i f 1-- •-Thi I I ; l I 80 - I I -� I I -;_ �� - i_i_ �_I 1�i l -i I 1 1111 1 i -L-- -I I - i 60 l j ` i ! 1 i I J . m 40 , I Lt_I l i L. i i L- a i I j 1 I �_ 1 - 20 i I1 ! tt I I-I 1- r I ' 1 i C' I II it I I i _ _ 1 100 a 10 1 0.1 0.01 Gravel Sand Silt and Clay Coarse Fine Coarse Medium Fine i Grain Size,mm ASSOCIATED EARTH SCIENCES, INC. 911 5th Ave,Suite 100 Kirkland,WA 98033 425-827-7701 FAX 425-827-5424 GRAIN SIZE ANALYSIS - MECHANICAL • Date Project Project No. Soil Description • 04/22/2011 Nelsen Middle School KE110083A Sand with gravel trace silt Tested By Location EB/EP No Depth Intended Use/Specification MS Onsite EB-9 30' Wt.of moisture wet sample+Tare 1018.06 Total Sample Tare 521.15 Wt.of moisture dry Sample+Tare 986.65 Total Sample wt +tare 986.65 Wt.of Tare 521.15 Total Sample Wt 465.5 Wt.of moisture Dry Sample 465.5 Total Sample Dry Wt 436.1 Moisture% 7% Specification Requirements Sieve No. Diam.(mm) Wt. Retained (g) % Retained % Passing Minimum Maximum 3 76.1 0.0 100.0 - - 2.5 64 0.0 100.0 - - 2 50.8 0.0 100.0 - - 1.5 38.1 0.0 100.0 - - 1 25.4 32.3 7.4 92.6 - - 3/4 19 32.3 7.4 92.6 - - 3/8 9.51 77.14 17.7 82.3 - - #4 4.76 130.66 30.0 70.0 - - #8 2.38 198.59 45.5 54.5 - - #10 2 214.6 49.2 50.8 - - #20 0.85 297.49 68.2 31.8 - - #40 0.42 363.73 83.4 16.6 - - #60 0.25 390.84 89.6 10.4 - - #100 0.149 407.18 93.4 6.6 - - #200 0.074 420.17 96.4 3.6 - - #270 0.053 425.44 97.6 2.4 - - US STANDARD SIEVE NOS. 3/4" NO4 N0.16 NO40 NO200 100 - C I j1 1i ' 1ll I rI FT i ___;_ I - - i - 1 1 I -I - ISo I i _4! I - I _ - I ' L I L -I -_4-I-. I I C I i I I ( I i--i--- - `I I i i i V I I I r 1 I I I j i w 40 I t i - _ - , _I ! I I illi I i ii f ,i1 j _ ; - 0 1 i I I I I i I i _ Hill , ; i 1 i i D i1. 100 10 1 0.1 0.01 Gravel Sand Silt and Clay Coarse Fine Coarse Medium Fine Grain Size,mm ASSOCIATED EARTH SCIENCES, INC. 911 5th Ave,Suite 100 Kirkland,WA 98033 425-827-7701 FAX 425-827-5424 • GRAIN SIZE ANALYSIS - MECHANICAL • Date Project Project No. Soil Description 04/29/2011 Nelsen Middle School KE110083A Sand with silt little gravel Tested By Location EB/EP No Depth Intended Use/Specification MS Onsite EB-13 5' Wt.of moisture wet sample+Tare 294.63 Total Sample Tare 395.59 Wt.of moisture dry Sample+Tare 274.81 Total Sample wt +tare 751 Wt.of Tare 99.3 Total Sample Wt 355.4 Wt.of moisture Dry Sample 175.51 Total Sample Dry Wt 319.3 Moisture% 11% Specification Requirements Sieve No. Diam. (mm) Wt. Retained (g) % Retained % Passing Minimum Maximum 3 76.1 0.0 100.0 - - 2.5 64 0.0 100.0 - - 2 50.8 0.0 100.0 - 1.5 38.1 _ 0.0 100.0 - - 1 25.4 0.0 100.0 - - 3/4 19 13.8 4.3 95.7 - - 3/8 9.51 27.12 8.5 91.5 - - #4 4.76 48.05 15.0 85.0 - - #8 2.38 65.26 20.4 79.6 - #10 2 69.22 21.7 _ 78.3 - - #20 0.85 87.14 27.3 72.7 - - #40 0.42 118.61 37.1 62.9 - #60 0.25 163.43 51.2 48.8 -- - #100 0.149 195.96 61.4 38.6 _ - - #200 0.074 218.37 68.4 31.6 - - #270 0.053 226.68 71.0 29.0 - - US STANDARD SIEVE NOS. 3/4" NO 4 NO 16 NO 40 NO 200 100 --'a 0 0 p rf, • I , 80 i - IJ-I pp- i i ! ' j I I I I l I f 60 d 40 I l ' 1 a_i J I - T� I I � I 20I _ (�-' -�_ I ii _ iii 0_ � 1I ! IIII ii i111i i 100 10 1 0.1 0.01 Gravel Sand Silt and Clay Coarse Fine Coarse Medium Fine Grain Size,mm ASSOCIATED EARTH SCIENCES, INC. 911 5th Ave,Suite 100 Kirkland,WA 98033 425-827-7701 FAX 425-827-5424 Associated Earth Sciences , Inc . _ Percent Passing #200 ,^== 01 111 ASTM D 1140 Date Sampled Project Project No. Soil Description 04/22/2011 Nelsen Middle School KE110083A Tested By Location EB/EP No.Depth Sand with silt MS Onsite Sample I.D. EB-11 2.5' EB-12 2.5' Wet Weight 891.7 825.5 Dry Weight 827.4 751.0 Water Weight 64.4 74.5 Pan 31 298.2 Actual Dry Weight 513.5 452.7 Percent of Water Weight 12.5 16.5 After Wash Weight 662.8 614.1 Percent Passing#200 32.0 30.2 ASSOCIATED EARTH SCIENCES, INC. 911 5th Ave,Suite 100 Kirkland,WA 98033 425-827-7701 FAX 425-827-5424 ,Associated Earth Sciences , Inc . Moisture Content ASTM D 2216 m e 1-.4,11 .1, vi 6,,,ii Date Sampled Project Project No. Soil Description 04/22/2011 Nelsen Middle School KE110083A Tested By Location EB/EP No. Depth Various MS Onsite Sample ID EB-5 2.5' EB-10 5' EB-11 2.5' Wet Weight + Pan 465.4 562.7 361.0 Dry Weight + Pan 435.3 521.4 330.5 Weight of Pan 99.3 100.1 101 6 Weight of Moisture 30.1 41.3 30.5 Dry Weight of Soil 336.0 421.3 228.9 Moisture 9.0 9.8 13.3 Sample ID EB-11 15' EB-12 2.5' Wet Weight+ Pan 495.9 281.5 Dry Weight+ Pan 459.4 260.6 Weight of Pan 100.8 94 9 Weight of Moisture 36.5 20.8 Dry Weight of Soil 358.6 165.8 Moisture 10.2 12.6 ASSOCIATED EARTH SCIENCES, INC. 911 5th Ave,Suite 100 Kirkland,WA 98033 425-827-7701 FAX 425-827-5424 I